Excess-current cut-out



Aug. 26. 1924 L. HAAG' EXCESS CURRENT CUT-OUT Filefii May 11 1922 my W a n O H w t o n d u e v A v 8 mm o H 8 1M y y ID INA 2 AHI VMWW WWW Q Ji Patented Aug. 26, 1924.

UNlTED STATES PATENT OFFICE.

LEONHARD HAAG, OF BERLIK-ZEHLENDGRF, GERMANY, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A G-JBPORATIGN OF NEW YORK.

EXCESS-CURRENT CUT-OUT.

Application filed Kay 11,

To all whom it may concern:

Be it known that I, LEONHARD Hans, a citizen of Germany, residin at Berlin- Zehlendorf, Germany, have invented certain new and useful Improvements in Excess-Current Cut-Outs, for which I have filed an application in Germany, February 11, 1921, of which the following is a specification.

The demand for an excess current cut-out or circuit interrupter which automatically opens when the current in the controlled circuit is above a predetermined value has given rise to the development of various forms of high speed circuit interrupters which are intended to fulfill the requirements. A well known circuit interrupteroi this kind has a circuit controlling switch member which is connected with an armature of electromagnetic controlling means ar ranged to hold the switch member in the closed position against its bias to the open position by the magnetic pull of a shunt winding which operates against the pull of a spring or some other arrangement. A se ries winding is also provided which is arranged in such a manner that the flux of the series winding opposes the holding effect of the flux of the shunt winding, so that when the current through the series winding exceeds the predetermined value, the holding effect of the shunt winding visdiminished and the switch member is permitted to resume the open position in accordancewith its bias.

One of the problems involved in-circuit interrupters of this nature is that of taking care of the variation in the flux of the shuntv holding coil while the current is rapidly increasing in the series releasing coil. Where the paths for the fluxes of theshunt of the series windings are interlinked, there is an electromotive force generated in the shunt coil due to the rapidly increasing current in the series coil and a magnetic flux is thus set up which tends to reduce the speed of opening ofthe circuit interrupter. Furthermore, another problem is involved in that by reason of the fact that the current in the series coil increases very rapidly under extreme conditions as, for instance, short circuit conditions, there is apt to be a very quick re- ,versal of the magnetism through the armature or other movable magnetic member connected to the switch member, and the arms 1922. Serial R0. 560,213.

ture is thus apt to be magnetically held in the closed position. The spring or other device which biases the switch member to the open position is thus rendered ineffective to release the switch member and open the controlled circuit.

One of the objects of my invention is to provide an improved excess current cut-out or circuit interrupter which shall obviate the above mentioned disadvantages. Another object of the invention is to rovide a quick acting circuit interrupter w ich shall in addition to obviating the disadvantages pointed out above have the further advan tage of simplicity of construction and arrangement, and to be soconstructed that with a very quick increase of the current in the circuit controlled by the switch, the circuit interrupting movement is started before the current in the controlled circuit has reached the predetermined maximum value for ordinary overloads.

The invention will be understood from a consideration of the accompanyin drawings when taken in connection with 51c following description. Referring to the drawings, Fig. 1 shows in very diagrammatic form an arrangement of electromagnetic controlling means for a circuit interrupter designed to elfect a quick release of the holding electromagnet when the current in the circuit controlled by the switch exceeds a predetermined value; Fig. 2 is. a very simplified diagram of a circuit interrupter in accordance with the invention; and Fig. 3 is a very simplified diagram of a modified and improved arrangev mentfor the circuit interrupter illustrated in Fig. 2.

Referring to Fig. 1, the eneral idea of this arrangement is that o compensating for the undesirable self-induction of the shunt winding when the current through the series coil increases rapidly, by connecting in series with the shunt coil another shunt coil in which there is simultaneously induced an electromotivc force which is in the opposite direction to the self-induced electromotive force of the first shunt coil. The relative values of the self-induction of the first shunt coil and of the electromotive force induced in the second shunt 0011 may be so chosen that according to the require ments, either complete compensation or an excess compensation for the induced voltage may be effected. The two shunt coils 0, and 0 are disposed on separate magnetic struc tures a and a and the series coils g, and g, are disposed on the respective magnetic structures so as to control the flux through the magnetic structures. The shunt coils c and c, are connected in series relation, and the current through these coils flows in such direction through the respective coils that the flux of the coil 0 is in one direction through its magnetic structure a, and the flux of the shunt coil 0 is in the opposite direction through its magnetic structure (1 The series coils g and 9 are also connected in series, but the flux of the coil 9 through the magnetic structure a is in the same direction as the flux of the coil 9 through the magnetic structure a WVith this arrangement, the self-induction which occurs in the .shunt coil 0, is compensated for by the electromotive force generated in the shunt coil 0 because of the fact that the induced voltages of the two shunt coils will be in opposite directions.

By combining the magnetic structures a, and a the coils g and 9 the coils 0 and c of the arrangement of Fig. 1, and making various changes, there is obtained .a quickacting circuit interrupter as shown in Fig. 2. In the arrangement of this figure, the self-induction of the shunt coil, which is caused by anincrease in the current. in the series coil, is suppressed by the arrange ment of the magnetic structure. In the arrangement of Fig. 1, the magnetic paths are entirely separated, but in the arrangement of Fig. 2 these paths are combined by reason of the fact that there is a common magnetic structure. The magnet a of this arrangement consists of a double T-shaped ma netic structure with the shunt winding 0 disposed on the portion or core 5. There are two multiple connected magnetic paths for the flux of the shunt winding 0, the one path being through the right hand portion of the magnetic structure and the magnetic movable member or armature (Z which coope'rates with the oles of this right hand portion, and the ot er path comprises the left hand portion of the magnetic structure with the part f on which the series winding 9 is is disposed. The part 7 is separated by an air gap e which may be adjusted in order to adjust the action of the series winding 9 in eifecting an interruption of the controlled circuit. Each of the said paths is formed in part, at least, of magnetic material. The armature ti may be hinged, as shown, and connected to the switch member h, and the armature and switch member are biased to the open position by the action of the spring 2'. The contact brush is carried by the switch member h and cooperates with stationary switch contact as mum. in order to complete the circuit co..-.rolled by the switch. The electromagnetic blowout arrangement comprises the arcing horns Z and m and the blowout coil n.

The magnetic flux set up by the shunt coil 0 will have two multiple connected paths, one path being through the armature (Z and the other path being through the yoke or part of magnetic material f, as long as the series coil 9 is deenergized or the current through this coil is at a substantially normal value. The division of the flux through the two multiple connected paths will be in accordance with the magnetic reluctance of the two paths. Therefore, as long as the magnetic flux through the armature d is a substantially normal value, the switch member will be maintained in the closed position against the action of the spring-2' tending to open the switch. The series coil 9 is connected in such a manner that an increase in current in the series coil will cause the magnetic flux through the core I) tobe increased and the flux through the armature d to be decreased. In other words, the reluctance of the leakage path will be decreased while the flux through the armature is being re duced. Thus, when the current in the circuit controlled by the switch increases, the number of lines of force in the right hand path traversing the armature (i will be decreased so as to permit the switch member to open in accordance with its bias, and the number of lines of force enclosed by the shunt winding will be increased. The core on which the shunt winding is disposed is normally in an unsaturated condition, and is so proportioned as to become saturated when the current through the series coil exceeds the predetermined maximum value. Every increase of the density of the lines of force in the yoke or part f caused by the increase of the current in the coil. 9 will cause a corresponding reduction of the lines of force in the right hand magnetic circuit which includes the armature d. The fluxes of the shunt and the series windings will be in the directions indicated by the arrows. If the density of the lines of force through the armature (i is suiliciently reduced due to the increase of current through the series coil, the switch member will be permitted to automatically and quickly return to the open position under the action of the spring i. If the current in the circuit controlled by the switch increases very quickly, then the shunt coil will act as a choking coil, in consequence of which the additional magnetic flux set up by the series coil in the left hand portion. of the magnetic circuit. including the part will pass priucipally through the a 'anature (Z and a comparatively small. ream; will through the core The saturated conditi through the armature d is reduced so much that it is released before the flux through the core 6 reaches its saturated condition, and the controlled circuit will therefore be automatically, opened before the current in the controlled circuit has reached the predetermined maximum value for ordinary overloads. A quick interruption of the controlled circuit is thereby effected. If necessary or desirable, a short circuiting coil may be disposed on the core 2') in order to cause the principal portion of the flux from the series coil to act in opposition to the flux of the shunt coil through the armature d. The cross section of the yoke or part f is so chosen that even with the highest value of current through the series coil such as would be occasioned under short circuit con ditions, there wi l be no reversal of the polarity of the poles of the magnetic structure a with which the armature d cooperates, or if there is a reversal of magnetism, it will be of such a limited value that the armature will not be magnetically held in the closed position under short circuit conditions. It for any reason the shunt coil is deenergized, the armature will not be held in the closed position by the action or the series coi. That is because of the fact that the core 6 will form a leakage path for the flux of the series coil, and this leakage path will be of lower reluctance than the path through the armature. By varying the air gap 6, the switch may be adjusted to interrupt the controlled circuit at any predetermined value of current.

In Fig. 3 there is illustrated a modification of the arrangement of Fig. 2. The combination of two paths of magnetic material for the shunt coil is obtained in this arrangement by dis osing each of the shunt coils a and c, on t e shanks of the horseshoe magnet a and arranging the magnetic circuits in such a manner that the series coil 9 is disposed on a leakage yoke or part 7 which is disposed between the poles of the magnetic structure a, and forms a leakage path for the flux of the shunt winding in multiple with the path for the flux through. the armature d. The part f is separated from the magnetic structure a, Fo an air gap in the manner similar to the arrangement of Fig. 2. Two shunt coils c and 0,, are provided, but obviously these coils may be replaced by a single coil having the same efi'ect as the two coils c and 0 The arrangement is essentially the same as that shown in Fig. 2, and the principle of opera tion is the same. When the current in the controlled circuit increases ahove the pre determined value, the flux through the armature of will be reduced, and the fins. which passes through the portion of the magnetic circuit embraced by the shunt coil or coils will be increased, The part will he portioned so as to be normally in an unsaturated condition, and become saturated when the current throu h the series coil exceeds the predetermine value to prevent the building up of a flux in the reverse direction in the holding armature and around through the magnetic structure between the poles of the holdin electromagnet, so that there will be no ten ency to retard the opening movement of the armature and the switch contact due to the magnetic pull of a flux in the reverse direction. The magnetic movable member or armature 0? will he connected to the movable switch memher as in the arrangement of Fig. 2. It is believed that with the explanation of the features of construction and principles of operation previously given in connection with Fig. 2, the operation of the arrangement of Fig. 3 will be apparent to those skilled in the art. The arrangement of Fig. 2 has the advantage that a simpler form of magnetic structure may be used. The short circuited winding 0 may be disposed on the portion of the magnetic circuit embraced by the shunt coil or coils in order to further accelerate the interruption of the controlled eircuit in the manner explained in connection. with the similar coil provided in the arrangement of Fig. 2.

In switches of this nature which are designed for use with very high currents, it is preferable to energize the series coil proportionately to the current in the controlled circuit rather than to cause the entire current the controlled circuit to pass through the series coil. in such a case it may be advisable to provide an inductance which will at least equal the inductance of the series coil, and be disposed with relation to the series coil so that when there is a sudden increase in the current in the controlled circuit the current in the series coil will increase at least as fast as the current in the controlled circuit. If this inductance is greater than the series coil, the current will increase in the series coil at a greater rate than the current in the controlled circuit, so that an accelerated release of the switch member may be thereby efrec ted,

In accordance with the provisions of the patent statutes, I have described the principle of operation of m invention, together with the apparatus w ich I now consider to represent the best embodiment thereof, but i desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means. I

What I claim as new and desire to secure by Letters Patent of the United States, 1s:

1. An interrupter for electric circuits comprising a switch member biased to the open position, an electromagnet having a shunt winding and a magnetic structuretherefor having two poles, a magnetic movable member connected to the said switch member and cooperating with the said poles for holding the switch member in the closed position, a part of magnetic material disposed between the said poles and between the said magnetic movable member and the said winding, and means energized responsively to the current through the switch disposed with relation to the said part of magnetic material for reducing the flux through the said magnetic movable member to permit the switch rnemberto open in accordance with itsbias.

2. An interrupter for electric circuits comprising a switch member biased to the open position, an electromagnet having a shunt winding and a magnetic structure therefor having two poles, a magnetic movable member connected to the said switch member and cooperating with the said poles for holding the switch member in the closed position, a part of magnetic material disposed between the said poles and between the said magnetic movable member and the said winding and separated from the said magnetic structure by an air gap, and means energized responsively to the current through the switch disposed with relation to the said part of magnetic material for reducing the flux throughvthe said magnetic member to permit the switch member to open in accordance with its bias.

3. An interrupter for electric circuits comprising a switch member biased to the open position, an electromagnet having a shunt winding and a magnetic structure therefor having two poles, a magnetic movable member connected to the said switch member and cooperating with the said poies for holding the switch member in the closed position, a

part of magnetic material disposed between the said poles and between the said magnetic movable member and the said winding, and a.coil energized responsively to the current through the switch disposed on the said part of magnetic material for reducing the flux through the said magnetic movable member to permit the switch member to open in accordance with its bias, the said part of magnetic material being normally in an unsaturated condition and so proportioned as to become saturated when the current in the said coil exceeds a predetermined value.

4. An interrupter for electric circuits comprising a switch member biased to the open position, an electromagnet having a shunt winding and a magnetic structure therefor having two poles, a magnetic movable member connected to the said switch member and cooperating with the said poles for holding the switch member in the closed position, a part of magnetic material disposed between the said poles and between the said magnetic movable member and the said winding and separated from the said magnetic structure by an air gap, and a coil energized responsively to the current through the switch disposed on the said part of magnetic material for reducing the flux through the said magnetic member to permit the switch member to open in accordance with its bias, the said part of magnetic material being normallyin an unsaturated condition and so proportioned as to become saturated when the current in the said coil exceeds a predetermined value.

In testimony whereof I afiix my signature 26th day of April, 1922,

LEGNHARD HAAG.

Witnesses:

WILLIAM E. LANE, Earn Roos'rme, 

